package com.yulan.Array;

import org.junit.Test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * 15. 三数之和
 */
public class LeetCode_15 {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> ans = new ArrayList<>();
        int len = nums.length;
        if( len < 3) return ans;
        Arrays.sort(nums);
        for(int i = 0; i < len; i++){
            if(nums[i] > 0 )break;
            if(i>0 &&  nums[i] == nums[i-1]) continue;
            int l = i + 1;
            int r = len - 1;
            while(l<r){
                int sum = nums[i] + nums[l] + nums[r];
                if(sum == 0){
                    ans.add(Arrays.asList(nums[i], nums[l], nums[r]));
                    while(l<r && nums[l] == nums[l+1]) l++;
                    while(l<r && nums[r] == nums[r-1]) r--;
                    l++;
                    r--;
                }else if(sum > 0 ){
                    r--;
                }else{
                    l++;
                }
            }
        }
        return ans;
    }

    @Test
    public void test(){
        int[] arr = {-1, 0, 1, 2, -1, -4};
        for(List<Integer> list : threeSum(arr)){
            System.out.println(list);
        }
    }
}
